Issue 4591: custom isUrl must override internal links

Tracker

• Source type: GitHub issue
• Source id: #4591
• Title: don't want insert internal links starting with /
• URL: https://github.com/udecode/plate/issues/4591
• Task type: bug
• Expected outcome: a user-provided isUrl option can veto autolinking for internal paths like /aaa and anchor links like #top, while the default link behavior still accepts those shortcuts when no custom override is provided
• Browser surface: no; the stable seam is packages/link URL validation and paste/autolink tests

Relevant area

• packages/link/src/lib/utils/validateUrl.ts
• packages/link/src/lib/utils/validateUrl.spec.ts
• packages/link/src/lib/BaseLinkPlugin.ts
• any paste/autolink tests that prove the user-facing behavior, if needed

Learnings

• Current main still returns early for /... and #... before consulting isUrl, so the issue is still real
• platejs default isUrl returns false for /aaa and #top, so a naive reorder would break the plugin's intended internal-link and anchor-link shortcuts
• Recent link-validation work already had to special-case / handling to exclude //; this fix should stay minimal and avoid reopening that regression

Plan

1. Add a failing validator test that proves custom isUrl cannot currently veto /... and #....
2. Implement the smallest fix that only gives priority to custom isUrl, not the default platejs validator.
3. Re-run targeted tests for packages/link.
4. If the fix is meaningful and verified, create/update the PR and post back to the issue.

Progress

• Fetched the issue and comments.
• Read the task, planning-with-files, learnings-researcher, and tdd skill docs.
• Searched docs/solutions and read the recent link-validation learning about // internal-path regressions.
• Verified validateUrl still bypasses custom isUrl for /... and #....
• Confirmed the old Claude branch exists remotely, but there is no PR for #4591.
• Checked out main, pulled latest, and branched to codex/4591-custom-isurl-internal-links.
• Added red coverage in validateUrl.spec.ts and upsertLink.spec.tsx, then confirmed current main failed those expectations.
• Updated validateUrl so only custom isUrl overrides can veto /... and #..., while the default platejs validator still preserves existing internal-link and anchor-link behavior.
• Verified with:
  • bun test packages/link/src/lib/utils/validateUrl.spec.ts packages/link/src/lib/transforms/upsertLink.spec.tsx packages/link/src/lib/withLink.spec.tsx
  • pnpm install
  • pnpm turbo build --filter=./packages/link
  • pnpm turbo typecheck --filter=./packages/link
  • pnpm lint:fix
• Added .changeset/link-custom-isurl-internal-links.md.

Errors

• planning-with-files session catchup script path from the generated skill is missing locally, so catchup could not run in this repo.